Thread tension device for sewing machines



Feb. 8, 1955 s. J HAMLETT 2,701,694

THREAD TENSION DEVICE FOR SEWING MACHINES Filed March 20, 1952 2Sheets-Sheet l "HGHTS 7/ 4/ E? I fie? 5 INVENTOR.

570 5 JAhMM-rr 14 rro ENE 5 Feb. 8, 1955 J. HAMLETT 2,701,694

THREAD TENSION DEVICE FOR SEWING MACHINES Filed March 20, 1952 2Sheets-Sheet 2 Arraemsys United States Patent THREAD TENSION DEVICE FORSEWING MACHINES Sidney J. Hamlett, Pat-ma, Ohio, assignor to WhiteSewing Machine Corporation, Lakewood, Ohio, a corporation of DelawareApplication March 20, 1952, Serial No. 277,621

12 Claims. (Cl. 242-150) This invention relates to thread tensioningdevices and, more particularly, to a mechanism for use on a sewingmachine to subject the .thread utilized therein to a preselected tensionwhich may be readily varied.

The principal object of the invention is to provide an improved meansfor tensioning the thread in a sewing machine, which means is economicalto manufacture, easily installed, reliable in action, and easilyadjusted by the user to provide a wide range .of thread tensions.

A more specific object of the invention is to provide an improved meansfor .tensioning the thread of a sewing machine such that any desiredthread tension within a wide range of values thereof can be secured byrotation .of a single member through less than one revolution, thepreselected tension being reliably maintained against unwantedvariations during sewing operations.

A still more specific object .Of the invention is to provide an improveddevice for tension-ing the thread of a sewing machine by means of aspring and abutting members aligned with the tensioning disk-likemembers between which the thread passes, the pressure on the thread, andhence the tension thereof, being varied by .at least one of theinterengaging surfaces of the abutting members having an axiallydirected cam portion so that partial rotation thereof provides acomplete range .of desired thread tensions.

Another object of the invention is .to provide an improved threadtensioning device as defined above with a means for releasing thepreselected thread tension upon elevation of the presser foot bar of thesewing machine without altering the angular position of the rotatabletension adjusting member so that restoration of the pres- .ser foot barto its lower position reestablishes the preselected tension on thethread.

The invention further resides in certain novel features of theconstruction and arrangement of the parts of the mechanism, and furtherobjects and advantages of the invention will be apparent to thoseskilled in the art to which it pertains from the following descriptionof the present preferred embodiment thereof, which is described withreference to the accompanying drawings in which:

Fig. 1 is a front elevational view of the present .pre ferred embodimentof the invention showing the manner in which it is applied to a sewingmachine head, only a portion of the latter being illustrated;

Fig. 2 is a transverse sectional view taken substantially on theirregular line 22 of Fig. 1 with certain conventional portions of thesewing machine omitted;

Fig. 3 is a fragmentary sectional view taken substantially on the line33 of Fig. 2;

Fig. 4 is an enlarged view in section through the device, the view beingtaken substantially on the line 44 of Pi 1;

i ig. 5 is a rear elevational view of the tensioning device per seremoved from the sewing machine head;

Fig. 6 is a fragmentary sectional view through the mechanism, the viewbeing taken substantially on the line 66 of Fig. 4 but to a smallerscale;

Fig. 7 is a detached perspective view of the rotatable tension adjustingmember of the mechanism showing the annular cam surface thereon;

Fig. 8 is a side elevational view of the structure shown in Fig. 2 asseen from the left-hand side of that figure with the principal portionof the side housing cover or plate broken away; and

Fig. 9 is an enlarged rear view of the mechanism shown 2,701,694Patented Feb. 8, 1955 in Fig. 8 with portions of the sewing machine head.broken away to more clearly reveal the operating parts.

Referring first to .Fig. 4 of the drawings, it will be seen that thepresent preferred embodiment of the tensioning mechanism, which isgenerally designated 10, comprises a central support in the form of ashaft or stud 11, the rear end 12 of which is threaded while the forwardend is provided with a head 13 and cylindrical shoulder portion 14.Rearwardly of the cylindrical portion 14 and intermediate it and thethreaded portion 12, the shank of the support or stud 11 is cylindricaland preferably has a diameter substantially equal to the outsidediameter of the threads 12. On this shank portion of the support or stud11 is disposed a sleeve 15 which is preventedi from rotation relative tothe stud or shaft 11 by means of a pin 16 secured in the sleeve andextending into a milled groove 17 in the stud 11.

The cylindrical portion 14 of the shaft or stud 11 is provided withapair of cooperating disk-like members 18, 19 between which the thread,which is to be tensioned, passes. These disk-like members may bevariously constructed, but the member 18 is here shown as a solid metaldisk having a planar rear face and a convex forward face. The member 19is preferably hollow for a purposehereinafter described and hence isshown as formed of sheet metal with a planar forward face engaging theplanar face of the member 18 but with the outer edge of this side of themember 19 tapering rearwardly to facilitate the entrance of threadbetween the members 18 and 19. The members 18, 19 are preferably freelyrotatable upon the cylindrical portion '14 and at least the member 19 isslidable thereon.

The rear face of the disk-like member 19 is received in a circularrecess provided in the forward face of an annular member 20 which has anaxially extending cylindrical portion 21 supported upon theaforementioned sleeve 15 and releasa'bly secured to the latter by meansof a set screw 22, the point of which fits into a circumferentiallyextending groove 23 provided in the sleeve 15. The member 20 has anenlarged axial opening in the forward portion thereof providing achamber between the disk-like member 19 and the portion of the member 20which engages the sleeve 15. Within this chamber is'disposed the coiledportion of an auxiliary tension spring 24 which has its inner endreceived in an opening in the sleeve 15 to prevent rotation of thespring relative to the sleeve and the stud '11. The outer end portion ofthe spring 24 extends through the hollow part of 'the disk-like member19 and through a slotted opening in the side thereof as shown in Fig. 3with this outer end portion of the spring bent, as shown in Figs. 1 and3, to provide a loop 25 for receiving a portion of the sewing machinethread 26.

Journalled upon the forward part of the cylindrical portion of themember 20 is an annular member 27 which is rotatable for effectingadjustment of the tension on the thread 26 as will hereinafter beapparent. The forward face of this adjusting member 27 has a circularrecess therein in which is received the rear face of the radial flangedportion of the member 20 see Fig. 4. The rear face of the member 27 hasan axially extending portion, the outer surface of which is in the formof an annular cam inclined relative to the axis of the device. in theform of the mechanism here illustrated, the cam surface Zd issubstantially helical and the total rise thereof is accomplished in adistance less than half the circumference, the surface being duplicatedso that there are in effect two identical cam surfaces 28, 29 on themember 27, see Fig. 7. Engaged with the cam surfaces 28, 29 are axiallyextending portions 30, 3.1 of a member, generally designated 32, whichhas a transversely extending portion 33 slidably supported upon theshaft or stud 11.

The member 32 is normally held from rotation when the tensioning deviceis mounted in the head of the sewing machine by forming the portions 30and 31 as elongated legs which are received in individual recesses orgrooves 34, 35 in the head of the sewing machine. These recesses orgrooves extend parallel to and communicate with the opening in which themain body of the 'tensioning device is mounted while the widths of theseopenings or recesses are only slightly greater than the widths of theleg portions 30, 31 of the member 32, see Fig. 6. The forward ends ofthe portions or legs 3t), 31 engage with the aforementioned cam surfaces28, 29 on the member 27 and preferably are provided with cam surfacescomplementary to the surfaces 23, 25 for sliding cooperation therewith.The members 27 and 32 are held in engagement by a coiled compressionspring 36 disposed about the shaft or stud ll rearwardly of the member32 and intermediate the latter and a nut 37 which is screwed upon thethreaded end of the stud. nut 37 1s preferably held in any predeterminedposition by the lock ng action of the threads 12 of the stud, whichlocking action is effected in the illustrated embodiment by slotting theouter end of the support or stud 11 and slightly separating the twoportions adjacent the end thereof as will be readily understood.

In employing the apparatus as thus far described, the mechanism isassembled as shown in Fig. 4 and inserted in the prepared opening in thehead 38 of the sewing chine so that the legs 30, of the member aredisposed within the openings 34, 3S and the member 27 received, with aslight clearance, within a recess in the forward face of the head. Themechanism is secured in this position by means of a set screw 39threaded through the side of an integral boss 40 of the head 38, thepoint of the set screw being received in a recess in the side of themember intermediate the legs 38, 31 of the member 32, see Fig. 6. Thethread 26 to be used in the sewing machine is led through the usualguides, not shown, to and between the disk-like member 18, i9, thenceabout the loop of the auxiliary spring 24 and about a forwardlyprojecting thread guide 41 which is carried by a block 42 secured to thepresser foot bar 43 of the machine, see Fig. l. The thread 26 is thenled through the usual thread. takeup and thread guides to the needle inthe manner which is well understood and hence is not illustrated.

As thus disposed, the thread 26 will be placed under a predeterminedtension due to the pressure exerted between the members 18 and 19 byvirtue of the coiled spring 3.6 tending to move the shaft or stud llrearwardly, it beim remembered that the assembly is held from axialmovement as a whole with respect to the opening in the machine head bymeans of the set screw 39. The position of the nut 37 is initiallyadjusted before assembly of the device to provide a predeterminedminimum tension when the adjusting member 27 is disposed so that thelegs 30, 31''. engage the lowest portion or minimum positions of the camsurfaces 23, 29. This adjustment, which may be made at the factory or bya serviceman, is normally not. varied and is maintained by theabovemeutioned locking action. of the slotted end of the stud 11 whichexpands the threads thereof into gripping engagement with the threads ofthe nut 37.

The tension upon the thread 26 passing between the l members 18, 19 maybe varied through the desired range of values by the operator simplyturning the member 27 through a portion of a revolution, which in theillustrated embodiment is slightly less than half a complete revolution.The adjusted position of the member 27 and hence the resulting tensionon the thread may be visually indicated by suitable indicia 44 upon theflange of the member 2'7 which cooperate with a reference arrow orindicium 45 on the head of the machine. adjusting member 27 isfacilitated by virtue of the fact that. it is positioned adjacent a sideface of the sewing machine head 38 with the flange of the member 27extending slightly beyond the head, as is clearly shown in Fig. i, sothat the edge of this flange may be easily engaged by a finger of theoperator. Adjustment may be further facilitated by milling, chasing orltnurling the outer edge of the flange, if desired. The rotation of themember 27 is preferably positively limited within the arcuate extent ofthe cam surfaces 28, 29 by suitable limiting means as, for example, by astop pin such as 4-6 mounted in the head of the sewing machine andfitting within an arcuate recess 37 on the rear surface of the adjustingmember 27.

it will be evident, therefore, that by this mechanism a wide range ofthread tensions may be easily secured through manipulation of the member27 a distance of less than one-half a revolution, which tension ismaintained during operation of the machine without variation, since theinter-engaging carn surfaces on members 27 and 32 Turning of the are sodisposed that vibration of the machine does not tend to cause relativemovement therebetween. The ten sion upon the thread is further augmentedby the spring 24 and the extent of this tension is normally adjustedprior to assembling the device by angular positioning the sleeve 25relative to the member 2%) and then clamping these parts in theiradjusted positions by means of the screw 22.

The conventional presser foot bar 43 of the sewing machine is providedat its lower end with the usual presser foot, not here shown, which isadapted to be elevated when the material to be sewed is being positionedbeneath the needle. In accordance with this invention, the mechanism foreffecting elevation of the presser foot bar also effects an axial thrustupon the shaft or stud 11 in the direction releasing the tension uponthe thread 26 passing between. In addition, the thread guide 41 is alsoelevated. These operations are effected by a manually operable member 48which is pivotably secured to the rear portion of the machine head, asby means of a screw 49, and has a cam surface 48' engaging a rearwardlyextending pin Sli provided on a bracket member 51 that is carried by thepresser foot bar 43. The bracket member 51 has a laterally extendingportion 51 which has a substantially rectangular opening slidablyengaged upon a vertically extending guide bar 52 carried by the machinehead 38. Extending forwardly from the portion 51 of the bracket 51 is anarm the outer end of which is provided with a vertically inclined cammember 53 positioned adjacent the rear end of the stud or support 11,see Figs. 2 and 8.

it will be apparent, therefore, that upon rocking of the member 48 in aclockwise direction, as viewed in Fig. 9, the cam surface 43 engages thepin thereby elevating the bracket 51 and the presser foot bar so thatthe presser foot is raised from the work. Likewise, the bracket 42 whichis connected with the presser foot bar 43 is also elevated so that thethread guide 41 is correspondingly lifted. The elevation of the bracket51 also raises the cam 53 so that the inclined surface of the latterengages the end of the stud 11, forcing the latter forwardly against theaction of the spring 36 so that the pressure between the members 18 and19 is released.

When the presser foot is to be restored to its initial position themember 48 is returned to a position substantially as shown in Fig. 9 andwhich is determined by a stop 54 provided upon the removable end coveror plate 55 for the head. Restoration of the member 48 causes loweringof the presser foot bar under the action of the conventional spring, notshown, thereby lowering the thread guide 41 to its position as shown inFig. 1 and moving the cam 53 from engagement with the stud or support 11so that the spring 36 returns the parts to their initial positions shownin Fig. 4. Consequently, the predetermined tension upon the thread isrestored. Since the member 32 is held from rotation and the tensionrelease is efiected solely by an axial movement of the stud 11, thepreselected tension as determined by the setting of the adjusting member27 is not altered by repeated elevation and lowering of the presser footbar during use of the apparatus. The tension upon the thread may,however, be readily varied as aforementioned by simply turning theadjusting member 27 to place the indicium corresponding with the desiredtension in alignment with the arrow 45.

It will now be apparent that this invention provides an improved threadtensioning means for a sewing machine which is compact, easilymanufactured and installed, and which may be readily adjusted by themachine operator without the need of special tools. Moreover, the entirerange of thread tensions, which is equal to or greater than thatprovided by conventional devices is now achieved through rotation of theadjusting member 27 a distance of less than half a revolution.Furthermore, this adjustment may be effected by a single finger of theoperator, this being due both to the novel construction of the mechanismand its convenient location upon the head of the machine. It will alsonow be evident that the novel mechanism provides for release of thethread tension upon elevation of the presser foot and restoration of thepreselected tension without variation thereof when the presser foot isagain lowered.

Although certain specific constructional details have been hereinillustrated and described as incorporated in the preferred embodiment,it will be apparent that variations maybe made without departing fromthe principles of the invention. For example, it is not essential thatthe normally stationary member 32 be in the form as here shown with twospaced legs, but may be provided with only one such leg or may be in theform of a continuous annular surface complementary with the surface onthe adjusting member 27. In the latter construction suitable means suchas a set screw or the like could be employed to prevent rotation of themember 32. It will also be apparent that, while the disk-like threadtensioning member 18 has been shown as separate from the head 13 of thestud or shaft, this member may in some instances be simply the enlargedhead of the central supporting stud or shaft 11. These and othermodifications and adaptations of the apparatus will be readily apparentto those skilled in the art and consequently the invention is not to beconsidered as limited to the details of the construction herespecifically disclosed except as may be required by the spirit and scopeof the appended-claims.

Having thus described the invention, I claim:

'1. A thread tensioning device mounted on a support comprising a studhaving a head at its forward end and having the outer end of its shankthreaded with an unthreaded portion between, a disk on the unthreadedportion of the shank engaging said head, a second disk on saidunthreaded portion of said stud in engagement with the first disk andadapted to exert force on a thread passing between said disks, a sleevesurrounding a portion of the shank of said stud and held from rotationrelative thereto, a spring wire having one end portion coiled about saidsleeve and secured thereto with the other portion extending outwardlytherefrom and provided with an olfset portion for receiving the threadpassing between said disks, an annular member surrounding said sleeveand coiled portion of said wire and having a portion engaging saidsecond disk, means securing said member to said sleeve, means releasablysecuring said member to said support, an annular adjusting memberrotatably supported upon the first mentioned annular member and having acam surface on its rearward end, a member supported on said studrearwardly of said sleeve and held from rotation relative to saidsupport, the last-mentioned member having an inclined cam surfacecomplementary to the first-mentioned cam surface and abuttingly engagedtherewith, a nut on the threaded portion of said stud, and a compressionspring surrounding the shank of said stud intermediate said nut and thelast-mentioned member creating pressure between said disks, whereby thepressure between said disks and hence the tension on a thread passingtherebetween may be varied by turning said adjustable annular member.

2. A thread tensioning device as defined in claim 1 and wherein thetotal rise of said cam surfaces occupies less than one-half thecircumference of said annular adjusting member and means are provided tolimit the extent of rotation of said annular adjusting member to lessthan one-half revolution.

3. A thread tensioning device as defined in claim 2 wherein the saidannular adjusting member has a radial flange a portion of which extendsbeyond the side wall of the support on which it is mounted therebyfacilitating actuation thereof by the machine operator.

4. In a support having an opening therein, a thread tensioning devicecomprising a stud, a pair of disk-like members on said stud adjacent oneend of the latter and adapted to receive thread therebetween, at leastone of said members being axially slidable on said stud, abutment meanson said stud adjacent the other end thereof, a pair of cooperatingmembers supported on said stud between said abutment means and saiddisk-like members in a manner permitting axial movement between saidstud and said cooperating members, one of said cooperating members beingrotatable relative to said stud and having the end face thereof adjacentthe other of said cooperating members provided with portions ofdifferent axial extents forming cam surfaces, the other of saidcooperating members having circumferentially spaced portions extendingaxially of said stud parallel with the axis of the stud and with theends of said portions engaging the said cam surfaces, a compressionspring on said stud between said abutment means and the said othermember urging the said disk-like members together and the saidcooperating members into engagement, and

tioned within the confines of the axially extending portions of the saidother of the cooperating members with a part .of said spring wireextending outwardly therefrom and from said support and having an offsetportion for receiving the thread passing between the disk-like members.

:6. ,In a support with .an opening therein, a thread tensioning devicecomprising a stud, :a 'pair of disk-like members on said stud adjacentone .end of .the latter and adapted .to receive thread therebetween, atleast one of said members being axially slidable .on said stud, abutmentmeans on said stud adjacent the other end thereof, a pair of cooperatingmembers supported on said stud between said abutment means and saiddisk-like members in a manner permitting axial movement between saidstud and said cooperating members, one of said =cooperating membersbeing rota-table relative to said stud and having the end face thereofadjacent the other of said cooperating members provided with portions ofdifferent axial extents forming cam surfaces, the other of saidcooperating members having circumferentially spaced axially extendinglegs the ends of which engage the said cam surfaces, a compressionspring on said stud between said abutment means and the said othermember urging the said disk-like members together and the saidcooperating members into engagement, and means removably securing thetensioning device in said opening of said support with a portion of saidone of the cooperating members accessible externally thereof and withthe sides of the legs on the said other member engaging portions of thesupport to prevent rotation of said member, whereby the pressure betweenthe disk-like members and hence the tension on a thread passingtherebetween is adjustable by rotation of the said one cooperatingmember.

7. A thread tensioning device as defined in claim 6 and furthercomprising means to limit the extent of rotation of said one of. thecooperating members to less than one-half revolution.

8. A thread tensioning device comprising a stud having a head at itsforward end, support means nonrotatable relative to said stud andguiding said stud for axial movement, a first disk on the shank of saidstud and engaged by its head, a second disk slidable on said studbetween said first disk and said support means and adapted to engagesaid first disk to exert force on a thread passing between said disks,an annular adjusting member mounted on saidsupport means coaxiallytherewith and with said stud for rotation about said stud and held bysaid support means against axial movement, the rearward end of saidannular adjusting member containing a cam surface, the rise and fall ofwhich is axial of said stud, a second member nonrotatably supported foraxial movement relative to said stud and having a portion extendingparallel with the axis of said stud with its forward end engaging saidcam surface of said adjusting member, and a coiled spring engaging withabutment means on said stud and with said second member and exerting anaxial force on said stud in a direction rearwardly of said supportmeans, thereby engaging said disks together under springload, wherebythe pressure between said disks and, hence, the tension of a threadpassing therebetween can be adjusted by partial rotation of said annularmember to increase or diminish the load exerted by said coil spring.

9. A thread tensioning device comprising a stud having a head at itsforward end, support means nonrotatable relative to said stud, a firstdisk on the shank of said stud and engaged by its head, annular guidemeans nonrotatably supported by said support means for guiding axialmovement of said stud and containing a bearing surface at its forwardend, a second disk slidable on said stud between said first disk andsaid guide means, and adapted to be engaged at its rearward end by thebearing surface of said guide means, and at its forward end by saidfirst disk to exert force on a thread passing between said disks, anannular adjusting member mounted on said guide means coaxially therewithand with said stud for rotation about said stud and suitably heldagainst axial movement, the rearward end of said annular adjustingmember containing a cam surface, the rise and fall of which is axial ofsaid stud, a second member nonrotatably supported for axial movementrelative to said stud and having a portion extending parallel With theaxis of said stud with its forward end engaging said cam surface of saidadjusting member, and a coil spring engaging with abutment means on saidstud and with said second member and exerting an axial force on saidstud in a direction rearwardly of said guide means, thereby engagingsaid disks together under springload whereby the pressure between saiddisks and, hence, the tension of a thread passing therebetween can beadjusted by partial rotation of said annular member to increase ordiminish the load exerted by said coil spring.

10. A thread tensioning device as defined in claim 8 and furthercomprising a second coiled spring surrounding said stud and having aportion extending outwardly therefrom for engagement with a threadpassing between said disks, means preventing relative rotation betweensaid spring and stud, and means to vary the angular position of saidstud relative to said support means and said annular member to therebyalter the force exerted by said second spring upon a thread engagedtherewith.

11. A thread tensioning device as defined in claim 8 and wherein saidannular member has a radial flange a portion of which extends beyond theside wall of said support means on which it is mounted therebyfacilitating actuation thereof by the machine operator.

12. A thread tensioning device as defined in claim 8 wherein said flangeand the adjacent surface of said support means are provided withcooperating indicia representative of the tension exerted upon a threadfor any position of said annular member and means to limit rotation ofsaid annular member to less than one revoution.

References Cited in the file of this patent UNITED STATES PATENTS1,820,119 Chason Aug. 25, 1931 2,554,493 Heiser May 29, 1951 2,560,577Ivandick July 17, 1951 FOREIGN PATENTS 310,516 Great Britain Mar. 20,1930 369,851 Great Britain Mar. 21, 1932 617,425 Germany Aug. 19, 1935370,672 Italy Apr. 26, 1939

